1. Field of the Invention
The present invention relates to optical semiconductor-based tube type lighting apparatuses.
2. Discussion of the Background
Generally, fluorescent lamps and incandescent lamps are used as a light source for lighting. Incandescent lamps have low economic feasibility due to high power consumption and thus demand for incandescent lamps continues to decrease. Further, it is predicted that this trend will continue into the future. On the contrary, fluorescent lamps have higher economic feasibility due to low power consumption, which is about ⅓ that of incandescent lamps. However, fluorescent lamps require application of high voltage, causing a blackening phenomenon and shortening the lifespan thereof. Further, mercury injected together with argon gas into a vacuum glass tube of a fluorescent lamp is toxic and environmentally unfriendly.
Recently, demand for LED lighting apparatuses employing an LED as a light source has rapidly increased. The LED lighting apparatus has long lifespan and requires low power for operation. Further, the LED lighting apparatus does not use a toxic substance such as mercury, thereby guaranteeing environmental friendliness.
Various kinds of LED lighting apparatuses having various structures have been developed. For example, a fluorescent lamp type or tube type LED lighting apparatus has a similar configuration to that of a fluorescent lamp.
FIG. 1 is a cross-sectional view of a conventional tube type LED lighting apparatus.
Referring to FIG. 1, the conventional tube type LED lighting apparatus includes an elongated light-transmitting cover 2 having a substantially semi-circular cross-section and open at an upper side thereof, and an elongated LED module 4 coupled to the open upper side of the light-transmitting cover. The LED module 4 includes an elongated heat sink 4a having a substantially semi-circular cross-section, a long printed circuit board (PCB) 4b attached to a flat surface of the heat sink 4a, and LEDs 4c arranged on the PCB 4b in a longitudinal direction. The LEDs 4c inside the LED module 4 emit light to the front of the lighting apparatus, that is, in a downward direction.
The conventional LED lighting apparatus emits light through an arcuate area in a predetermined angle range (in the range of about 120˜150 degrees) at a lower portion of the light-transmitting plastic cover 2. Further, since the back of the conventional tube type LED lighting apparatus is completely blocked by the heat sink 4a, light is not distributed to rear and lateral sides of the light-transmitting cover 2.
Such a conventional tube type LED lighting apparatus has very unsatisfactory light distribution characteristics as compared with existing fluorescent lamps. Accordingly, when the conventional tube type LED lighting apparatus is used in homes or offices instead of the existing fluorescent lamps, dark areas are generated at the rear and lateral sides of the lighting apparatus. Such dark areas cause user dissatisfaction as light coverage is uneven.
Such a conventional tube type LED lighting apparatus is configured to allow light to be diffusively emitted only through the semi-circular light-transmitting cover 2 and thus has lower light distribution characteristics than existing fluorescent lamps, which employ a light-transmitting tube. In addition, in the conventional tube type LED lighting apparatus, the LED 4c or the LED module including the LED 4c is located at the center of a tube-shaped cross-section defined by an outer periphery of the light-transmitting cover 2 and an outer periphery of the heat sink, thereby causing a short distance between a light emitting plane of the LED 4c and the light-transmitting cover 2 on a predetermined cross-sectional area of the tube type LED lighting apparatus. Since an area of the light-transmitting cover 2 through which light from the LED 4c passes decreases with decreasing distance between the light emitting plane of the LED 4c and the light-transmitting cover 2, the conventional tube type LED lighting apparatus has unsatisfactory light distribution characteristics towards the lateral and rear sides thereof.